Serum Serotonin Concentration is Elevated in Dogs with Degenerative Mitral Valve Disease
Little is known concerning the molecular mechanisms involved in degenerative mitral valve disease (DMVD). In humans, elevated serotonin (5-HT) is associated with development of valvular lesions. Canine mitral valve cells demonstrate dose-dependent 5-HT-mediated ERK1/2 signaling, suggesting a possible link with canine DMVD. We sought to measure serum 5-HT concentration in dogs with DMVD, dogs predisposed to DMVD (small breed dogs weighing <10kg and without a murmur), and healthy large breed control dogs. Measurement of 5-HT was performed using a competitive ELISA (IB89527, Immuno Biological Laboratories, Inc., Minneapolis, MN), which was validated for canine use. Seventy-nine dogs were enrolled (27 affected, 24 predisposed, and 28 controls), with 17/27 affected and 15/24 predisposed dogs being Cavalier King Charles Spaniels (CKCS). The assay demonstrated acceptable linearity (r=0.96), parallelism (P>0.05), and recovery (mean=100.9%). Analysis revealed significantly higher mean serum 5-HT in affected dogs vs. control dogs (affected, 650.6 [SD=232.9] ng/ml vs. control, 474.3 [210.4]; P<0.05), and in predisposed vs. control dogs (predisposed, 765.9 [322.8] vs. control, 474.3; P<0.001). Subgroup analysis revealed that predisposed CKCS had greater mean serum 5-HT than predisposed non-CKCS (CKCS, 903.9 [321.5] ng/ml vs. non-CKCS, 536.0 [153.7]; P=0.004). We conclude that dogs with clinically apparent DMVD as well as CKCS that are predisposed to DMVD have elevated serum 5-HT. Our results suggest that 5-HT may play a role in the development of DMVD in small breed dogs, and in particular in the CKCS. Further studies involving the relationship between 5-HT, DMVD, breed, and platelet number, morphology, and function are warranted.